Vehicle test fixture

ABSTRACT

A test fixture for an all-wheel drive vehicle provides a vertical hydraulic ram for each wheel position. Universal joint type connecting means are used to secure the vehicle atop the rams in the same way that the vehicle is secured to the wheels. Each connecting means, with its ram, permits 6* of movement to the wheel spindle to allow the spindle to move in accordance with the dictates of the wheel suspension geometry as the ram raises and lowers the wheel spindle to simulate irregularities in terrain. The fixture has input capabilities for fore-and-aft as well as transverse forces, and torque input to the wheel drives is provided for separate dynamometer loading of the wheel drives. The rear connection is shown provided with means to adjust the tapered roller bearings remotely, including a long-handle socket wrench which remains in place and is accessible after removal of the dynamometer connection, without disassembling the means by which the wheel spindle is mounted on the ram.

United States Patent [191 [111 3,828,614 [451 Aug. 13, 1974 Borg [VEHICLE TEST FIXTURE [76] Inventor: Henry A. Borg, 444 Morton St.,

Romeo, Mich. 48065 [22] Filed: July 12, 1973 [21] Appl. No.: 378,487

Related US. Application Data [62] Division of Ser. No. 312,418, Dec. 5,1972.

Primary Examiner-Leonard H. Gerin Attorney, Agent, or Firm-Edward J.Kelly;l-lerbert Berl; John Schmidt [57] ABSTRACT A test fixture for anall-wheel drive vehicle provides a vertical hydraulic ram for each wheelposition. Universal joint type connecting means are used to secure thevehicle atop the rams in the same way that the vehicle is secured to thewheels. Each connecting means, with its ram, permits 6 of movement tothewheel spindle to allow the spindle to move in accordance with thedictates of the wheel suspension geometry as the ram raises and lowersthe wheel spindle to simulate irregularities in terrain. The fixture hasinput capabilities for fore-and-aft as well as transverse forces, andtorque input to the wheel drives is provided for separate dynamometerloading of the wheel drives.

' The rear connection is shown provided with means to adjust the taperedroller bearings remotely, including a long-handle socket wrench whichremains in place and is accessible after removal of the dynamometerconnection, without disassembling the means by which the wheel spindleis mounted on the ram.

3 Claims, 8 Drawing Figures PATENTEU AUG 1 31974 SHEET 2 OF 7 PATENTEDMIG 131874 3.828.614

sum 3 or 7 PATENTED RUB 1 31974 3 828 614 sum 1; or 7 PATENTEU AUG 131914 SHEET 5 BF 7 I Fig-5 3328.614 I PAIENTED AUG 1 3 1914 I SHiEI 6 BF7 1 VEHICLE TEST FIXTURE This is a division, of application Ser. No.312,418, filed Dec. 5, 1972.

The invention described herein may be manufactured, used, and licensedby or for the Government for governmental purposes without payment to meof any royalty thereon.

BACKGROUND OF THE INVENTIO 1. Field of the Invention The inventionrelates to fixtures for the testing of fullsize, actual vehicles bysimulating terrain conditions likely to be encountered in operation ofthe vehicle.

2. Description of the Prior Art Much of the prior art approaches theproblem in terms of large drums to support the wheels. Such devices havesome value, because of course each drum can be connected to adynamometer, and the drums can be movably mounted. Nevertheless, thecontrollable drum approach has inherent limitations. For exam- SUMMARYOF THE INVENTION This invention provides means for a realistic testingof a full size wheeled vehicle. It should be remembered that, whilewheel movement is a function of variations in the terrain traversed, itis also a function of wheel suspension geometry. Thus, terrain featuresdictate whether the wheel moves up or down, and the forces imposed onthe wheel, while the suspension geometry dictates the manner in whichthe vehicle responds to terrain changes and those forces.

Accordingly, this invention provides each wheelwith six degrees offreedom so that the vehicle may respond to terrain changes in the mannerdictated by the suspension geometry.'For analytical purposes, thedegrees of freedom can be broken down into freedom for the wheel to movetranslatorily about three mutually perpendicular axes, andsimultaneously freedom to oscillate about each of said axes. Terrainchanges are simulated by means which impose forces on the vehicle asnearly identical as possible with actual forces.

More specifically, the test fixture comprises a plurality of supportsequal in number to the number of wheels. Each support is connected withthe vehicle in the same manner as the wheel-is normally connected withthe vehicle; in fact, the vehicle connection with the support takes theplace of the vehicle wheel and comprises a housing element with anelongated cylindrical bore which receives the wheel drive and connectswith the suspension in the same manner as the vehicle wheel; saidelement carries a shaft having an axis of rotation which is parallel tothe axis of said cylindrical bore. The shaft is slidable andoscillatable in one bore of a pillow block; resilient means center thepillow. block on the shaft, and the block in turn is provided with asecond bore at right angles to its first bore to receive a second shaftwith respect to which it is also slidable and oscillatable. The secondshaft is mounted in a yoke which is carried on a vertical ram; four suchrams, for a four-wheeled vehicle, constitute the aforesaid plurality ofsupports and they in-turn are an integral part of the buildingstructure, providing a vertical movement capability to simulate terrainirregularities, and other rams engage the vehicle connections to providecontrol capabilities along horizontal axes while dynamometers provideoscillatory inputs about the horizontal axes to simulate loading andterrain problems.

A housing element which receives a wheel drive provided with opposedaxial thrust bearings is desirably designed to facilitate adjustment ofthe axial spacing of the bearings with the vehicle in place on thefixture. To that end, a long socket wrench lying in the housing engagesthe spindle nut at its socket end, and the opposite end of the wrench isaccessible to a mechanic. The bearing adjustment is secured by setscrews placed to hold the wrench fixed against rotation relative tothespindle.

' IN THE DRAWINGS FIG.'1 is a schematic view of a complete testapparatus concept showing a test fixture in diagramatic form in abuilding structure.

FIG. 2 is a top plan view, partially schematic, showing the front andrear vehicle connections for the left side of a vehicle.

FIG. 3 is a view in elevation of the right front connection from. aposition between the ends of the vehicle and looking forward.

FIG. 4 is a rear elevation view of the left rear connection of the testfixture.

FIG. 5 is a side elevation view substantially from the plane of line 55of FIG. 4.

FIG. 6 is a sectional view on line 6-6 of FIG. 5.

FIG. 7 is a partial section of a wheel drive hub, showing how aconventional wheel hub is modified for use in the test fixture; and

FIG. 8 is view in section, substantially on line 88 of FIG. 2, through ahousing element to show how the dynamometer is connected to load thewheel drive, and how the opposed axial thrust bearings are adjusted.

THE PREFERRED EMBODIMENT The embodiment of the invention here shown isdesigned to test a four-wheeled vehicle. Accordingly, four substantiallyvertical supports 2, 4, 6 and 8 are shown mounted on a common baseindicated generally at 10. It should be understood that substantialloads and forces will be imposed upon and directed against base 10,which should be structurally capable of withstanding the loads. As hereshown, base 10 comprises a floor 12 and sidewalls secured theretothrough the building foundation or by other suitable conventionalarchitectural means. In FIG. 1, two walls 14 and 16 are shown, the othertwo being here omitted to avoid obscuring other, unconventional,details.

In the illustrated embodiment, each vertical support (2, 4, 6, 8) is ahydraulic ram, having a cylinder 18 secured to floor 12, and a pistonrod 20. To the upper end of each piston rod is secured means to connectthe sup port with a vehicle in the same manner as the completelyassembled vehicle carries a wheel. The connecting means are shownschematically in FIG. 1 at 22, 24, 26 and 28 at the upper ends of thepiston rods 20 of vertical supports 2, 4, 6 and 8 respectively.

Shown schematically at the top of the connecting means are housingelements 32, 34, 36 and 38 for supmanner as the wheels are mounted onthe vehicle, as

will be detailed below.

Because the object of the test fixture is to determine the effect onvehicle structure of the vehicles response to the terrain traversed, thetest fixture desirably allows each wheel spindle the freedom it requiresto move according to the dictates of the suspension geometry.Accordingly, each connecting means allows 6 of freedom of movement tothe wheel spindle. Three of the degrees of freedom are translatory,along three mutually perpendicular axes, and the remaining three areoscillatory, about said three mutually perpendicular axes.

Each of the degrees of freedom is represented diagrammatically in FIG. 1as a two-headed arrow. Of the translatory freedoms, probably the mostbasic is vertical movement because it is a by-product of gravitationalforces; the two-headed arrow representing vertical freedom of movementis identified by v for each vertical support.

Because the usual or normal direction of vehicle movement, fore-and-aft,generates many of the forces imposed on the vehicle, one of the mutuallyperpendicular axes is the fore-and-aft direction, represented by thetwo-headed arrow f in the diagrammatic showing of degrees of freedom inFIG. 1 in connection with each of the four vertical supports and theirassociated connecting means.

The third freedom of translatory movement is along an axis transverse tousual vehicle movement; such movement is induced by operating on a sideslope, centrifugal forces in a turn, and the like, and this third one ofthe three mutually perpendicular axes is identified by I'in FIG. 1 foreach vertical support.

One degree of freedom for each of the three mutually perpendicular axesis the freedom to oscillate about that axis (or about an axis parallelthereto). The twoheaded arrow 0,. is the one representing freedom tooscillate about axis v; o identifies the arrow representing freedom tooscillate about axisf; and 0, identifies the arrow representing freedomto oscillate aboutaxis t.

For a detailed discussion of the connecting means, reference is made tothe remaining figures of the drawing's. In FIG. 2, the connecting meansfor the left side of the test fixture are shown at 24 and 28 aligned onaxis XX which is substantially parallel to the direction of usualvehicle motion. The points of intersection A and B of axis XX with thewheel axes of rotation mark the center lines of the front and reartires, respectively. Those skilled in the art will understand that thefore-and-aft spacing of means 24 and 28 along axis XX is considerablyforeshortened as shown in FIG. 2.

The housing elements, referred to above and shown schematically in FIG.1 as cylinders 32, 34, 36 and 38 mounted atop connecting means 22, 24,26 and 28 respectively, appear in top plan in FIG. 2. Because FIG. 2shows only the left side of the vehicle test fixture, only the housingelements 34 and 38 appear in FIG. 2. It will be understood by thoseskilled in the art that connecting means 22 and 26 are substantiallymirror im- 4 is equally applicable to its corresponding mirror imagepart.

As is best seen in FIGS. 3-5, in the illustrated preferred embodiment,each housing element is formed integral with a bifurcated element whichmounts the ends of an elongated element. The elongated element engages acompound pillow block. By compound," I mean that this pillow blockprovides two bearing surfaces, each of which is cylindrical, and theaxes of the two cylinders are non-intersecting, at right angles to eachother. a

The aforesaid elongated element, here shown as a shaft, is mounted inone of the cylindrical bearings of the pillow block, as indicated above,and a second shaft, or elongated element, is mounted in the othercylindrical bearing. A second bifurcated element engages the ends of thesecond shaft and is mounted on its associated vertical support.Preferably, and as here shown, the compound pillow block is centered oneach shaft by resilient means.

Specifically, in FIG. 3, a bifurcated element 40 is secured to theunderside of housing element 32 by means of struts 42 and 44. Element 40engages the ends of elongated element (shaft) 46. Compound pillow block48 is mounted on shaft 46 and is preferably resiliently centered betweenthe ends of element 40 by any suitable resilient elastic means such asBelleville washers, helical springs, rubber bushings, or the like. Inthe embodiment illustrated, coil springs 50 are mounted between opposingfaces of block 48 and the ends of bifurcated element 40.

Similarly, FIG. 4 shows housing element 38 secured to a bifurcatedelement 52 by struts 54. Shaft 56 is held in element 52 and carries acompound pillow block 58, preferably centered by springs 60 between theends of bifurcated element 52.

FIG. 5 is a view from the right side of FIG. 4 and, as such, bestillustrates the second shaft and its relationship in the connectingmeans. As indicated above, pillow block 58 engages two non-intersectingshafts at right angles to each other: the aforesaid shaft 56, and

I a second shaft 62, of which the ends engage a bifurages of connectingmeans 24 and 28 respectively, and

that the description of details of one connecting means cated element.64. Coil springs 66 resiliently center block 58 between the ends ofelement 64.

Bifurcated-element 64 carries a stud 67 which has threaded engagementwith the upper end of piston rod 20 of vertical support 8. As is bestshown in FIGS. 5 and 5, element 64 is held against rotation relative torod 20 by a split ring and a pair of arcuate locks. More specifically, asplit ring is indicated generally at 68 and comprises half rings 70 and72 held together on piston rod 20 by screws 74. Piston rod 20 isprovided at its upper end with four flats 76 and half rings 70 and 72are correspondingly shaped.

Split ring 68 (the two half rings 70 and 72) is provided with a groove78. Arcuate locks 80 and 82 are secured to bifurcated element 64 byscrews 84 and closely adjacent to split ring 68. Set screws 86 in locks80 and-82 engage ring 68 in groove 78 and secure the locks and the splitring against relative rotation, and thus hold bifurcated element 64 andpiston rod 20 against relative rotation to keep element 64 (stud 67)from unscrewing and so becoming disconnected from rod 20.

It will be observed that accidental separation of element 64 and rod 20could be prevented without locks 80 and 82, simply by securing halfrings 70 and 72 to element 64 by means similar to screws 84. However, itis desirable that piston rod 20, at its upper end, tightly engage thelower face of element 64, better to withstand the severe forcestransmitted between thesetwo parts during test of a vehicle. Thearrangement I have shown is independent of any requirement for arealignment of the screw holes at the expense of such an aforesaid tightengagement. If, on dis-assembly, it should be found that half rings 70and'72 have been pierced to a significant depth by set screws 86, halfrings 70 and 72 as well as set screws 86 may readily be replaced by newparts.

Bifurcated elements 52 and 64 are capable of both translatory and rotary(or oscillatory) movement relative to compound pillow block 58. In thepreferred embodiment shown in this application, the ends of shafts 56and 62 are secured in bifurcated elements 52 and 64 respectively, and.the shafts engage compound pillow block 58 by means of conventionalbearings which allow the shafts to slide and to rotate in the pillowblock; it is that relationship that provides four of the 6 of freedom ofmovement hereinabove discussed.

More specifically, freedom of movement fore-and-aft is providedby thecapability for relative translatory movement between block 58 andbifurcated element 64, along the axis of shaft 62, as indicated by thetwoheaded arrow f in FIG. 5; freedom of movement to oscillate about theaxis of shaft 62 is due to the capability for relative oscillationbetween block 58 and bifurcated element 64, indicated by the arcuatetwo-headed arrow o in FIG. 4. Freedom of transverse movement is providedby the capability for relative translatory movement between block 58 andhousing element 38 (because housing element 38 is made integral withbifurcated element 52), along the axis of shaft 56, as indicated bytwo-headed arrow I in FIGS. 2 and 4; freedom of movement to oscillateabout the axis of shaft 56 is due to the capability for relativeoscillation between block 58 and housing 38 (or bifurcated element 52),shown by arcuate two-headed arrow 0, in FIG. 5.

The remaining two degrees of freedom of movement, namely translatorymovement vertically and oscillatory movement about a vertical axis, areprovided by the conventional piston-and-cylinder ram and the usual axisof the cylinder and the piston, wherein the piston I and rod are free toturn in the cylinder about their common axis; see two headed arrow v inFIGS. 4 and 5 and arcuate two-headed arrow 0,. in FIG. 6.

The front vehicle support connecting means 22 is described in detailabove only as to those elements including pillow block 48 and disposedabove block 48 as seen in FIG. 3, whereas rear connecting means 28 isdescribed in full in connection with FIGS. 4-6. It is pointed out thatpillow blocks 48 and 58 of FIGS. 3 and 4 respectively may be, andpreferably are, substantially identical, as are shafts 46 and 56 ofFIGS. 3 and 4 respectively. Moreover, the several parts of theconnecting means 22 including and disposed below block 48 in FIG. 3 aresubstantially identical to the corresponding parts in FIGS. 4 and 5,block 58 and below. Such identity is desirable so that parts may beinterchangeable.

As aforesaid, vertical supports 2, 4, 6 and 8 are hydraulic rams, eithersingle-acting for power lift and gravity return, or double-acting toprovide powerdown"'capability where that feature is desired. Thevertical supports are provided with a lift capability so that the testfixture may simulate the surface irregularities normally encountered inoperation. The most obvious effect of surface irregularities is ofcourse vertical motion of the wheels. However, such irregularities haveanother significant effect on vehicle structure. As the vehicle in itsforward motion, for example, causes a wheel to encounter either a bump(an obstruction above the ground) or a pobhole, the resulting force hasthe expected vertical component, but it also has a horizontal component.

In the test fixture here disclosed and claimed, means are provided tosupply the horizontal components, namely the fore-and-aft componentreferred to in the previous paragraph, and a transverse component to bedescribed below.

A fore-and-aft force input capability is provided by ears 88 on housing34 and cars 90 on housing 38. Force input connectors 92 and 94 are shownin engagement with ears 88 and 90 respectively. Each connector comprisesa pin 96, 'a universal joint assembly 98, and a socket element 100.Element is adapted by such means as a threaded socket 102 to receive oneend of any suitable conventional means for applying a reciprocatingtranslatory force, as for example a hydraulic ram, not shown in thedrawings. However, it will be understood by those skilled in the artthat one end of such a ram will engage element 100 and the other endwill engage the common base 10; more specifically, in the embodimenthere shown in FIG. 1, the rams providing fore-and-aft forces toconnecting means 26 and 28 will be suitably secured to wall 16 of commonbase 10, and to force input connectors 94 (FIG. 2) of each connectingmeans 26 and 28.

Similarly, vehicles are subjected to transverse forces due to operatingon a side slope, during turns, and for many other reasons. Some suchforces can be simulated by adjusting the vertical supports 2, 4, 6, 8 todifferent heights. However, the fixture may if desired be provided witha transverse force input capability. To that end, connecting means 22and 24, FIGS. 3 and 2 respectively, are provided with ears 104; as isbest seen in FIG. 3, ears 104 may be integral with the structure shownas housing 32, strut 44, and bifurcated member 40. Ears 104 will beprovided with force input connectors, one of which is shown at 106 inFIG. 2. FIG. 2 also shows ears 108, shown in FIG. 4 as formed integralwith the structure made up by housing 38, one of struts 54, andbifurcated member 52.

Conventional rams, not shown, will when their use is desired beconnected with ears 104 and 108 on the fixture and with the side walls,such as wall 14 in FIG. 1, of the common base.

The test fixture here disclosed and claimed has been built to testmilitary vehicles, which are often driven through more than one axle; inthis case, a fourwheel drive vehicle is contemplated. Loading of thewheel drives is often desirable, and means are illustrated to providesuch loading by dynamometers. Thus, FIGS. 3 and 4 show dynamometercouplings 110 and 112 fastened to the front and rear wheel drives,respectively.

It has been observed above that the test fixture connecting means carryhousings which are secured to the vehicle in the same manner as thewheels are secured to the vehicle. Thus, the front connecting means 22and 24 are provided with supports 114 and 116 for the upper and lowerball joints, respectively, and with left and rightsteeringarms 118 and120 respectively. The rear wheel suspension secures to the rearconnecting means in the same manner as to the. rear wheels, namely bythe rear suspension cap screws (not shown) engaging threaded openings122 in the end of housing 38.

Reference will now be made to FIGS. 7 and 8 for a description in detailof the means by which the rear dynamometer coupling is connected withthe wheel drive of the vehicle. Housing 38 is provided with a bore 124and the outer end of housing 38 is enlarged inside and out, as shown at126, which enlarged end supports a bearing bushing 128 tightly engagingthe bore as by a press fit. At its other end, the hollow housingsupports a pair of axially spaced tapered roller bearings 130 and 132which are the identical same bearings as those that support the vehiclewheel, not shown. The inner races of bearings 130 and 132 support a hub134; as shown in FIG. 8, hub 134 is a modification of a standard wheelhub.

FIG. 7 shows how a conventional wheel hub is modified to form a part ofthe illustrated test fixture. In FIG. 7, the upper half of the hub issectioned, and the lower half appears in elevation. The conventional hubis flanged as shown in dotted lines at 136; flange 136, in a vehicle,carries the studs to which the wheel is secured. In addition to thedotted line flange 136, there is shown, on the left of that flange, adotted line outside diameter of the hub which shows the hub in itsconventional outline. To adapt the conventional wheel hub to a hub foruse with the test fixture here, the portions appearing in FIG. 7 betweenthe dotted lines and the solid lines are machined away. 1

The hub portion on the right of flange l36 remains unaltered, and isprovided with two lands 138 and 140. Internally, the hub 134 has astepped bore of three diameters 142, 144, and 146, of which the portion144 is splined as shown.

The test fixture here disclosed and claimed is designed for a four-wheeldrive vehicle, of which the wheels are independently sprung orsuspended. Hub 134 is shown in FIG. 8 as rotatably mounted in housing 38by means of aforesaid opposed tapered, roller bearings 130 and 132 onlands 138 and 140 respectively. Bearings 130 and 132 thus support awheel spindle 148 in bore 124 of housing 38 and coaxial with said bore124.

Spindle 148 is a conventional wheel spindle of the vehicle that is to betested, and is here shown as comprising part of a universal joint 150, asmooth cylindrical surface 152, an externally splined surface 154adapted to engage internally splined bore 144, a threaded bore 156, anda nut 158 in threaded engagement with stud 156. The intersection ofbores 142 and 146, FIG. 7, forms a plane surface or shoulder 160 whichnut 158 reacts against through a washer 161. The other end of thereaction is the shoulder between smooth surface 152 and splined surface154, which engages the right face of bearing 132; more specifically, theshoulder on surface 152 engages the right face of the inner race ofbearing 132. The left face of bearing 130 is engaged by a face 162 onhub 134, face 162 being best shown in FIG. 7.

Smooth cylindrical surface 152 cooperates with a conventional oil seal164 which, along with spindle 148 and bearings 130, 132, is the sameidentical part that goes into the vehicle assembly. Oil seal 164 fits inthe extreme right end of bore 124.

Reference is made above to the diameter of hub 134, FIG. 7, to the leftof flange 136, and shown in dotted lines, which is machined downto forma cylindrical surface, indicated in solid lines as surface 166. A tube168 fully engages surface 166 and is welded to hub 134 at that surface.

At its left end as seen in FIG. 8, tube 168 carries a hub 170 and iswelded to the hub at its internal surface. A hardened steel wear collarI72 engages the external surface by means of a press fit. Collar 172ridesin bean ing bushing 128. Hub 170 carries a flange 174. Dynamometercoupling 112 is removably connected with flange 174 by means of threadedmembers 176 passing through openings in end plate 178 and engagingflange 174. Coupling 112 includes said end plate 178 and the portion 180of a universal joint. Elements 178 and 180 are secured together in anysuitable conventional manner so as to transmit torque between thedynamometer (not shown) and the wheel spindle 148, by way of said tube168 and its connecting elements.

Referring again to nut '158 on stud 156, provision is made for remotelyadjusting the axial play in bearings 130, 132 and their cooperatingelements. A longhandle wrench indicated generally at 182 has at one enda socket 184 which, in the finished assembly, remains in engagement withnut 158 as long as a vehicle is on the test fixture. At its opposite end186, wrench 182 is suitably polygonal for engagement by a wrench (notshown) in the hand of a mechanic who can reach end 186 after he or sheremoves dynamometer coupling 112.

Wrench 182 is supported at its right end by its engagement with nut 158.Because the wrench rotates with tube 168 during dynamometer test of thevehicle drive, the wrench should be substantially centered in the tube.At its left end, the wrench is located in a centering device 188comprising a hub 190 and a flange 192. A set screw 194 in hub 190 closeto its outer end is accessible to the mechanic to release wrench 182prior to adjustment and to secure it again thereafter.

Flange 192 is secured relative to tube 168 by means of one or more setscrews 196 which have threaded engagement with tube 168. Access toscrews 196 is through an opening in housing 38 which is normally keptclosed by a plug 198. Flange 192 is preferably provided with a pluralityof openings 200 to avoid the development of a pressure differentialacross the flange.

Operation It will be found convenient to equip the test fixture with anextra set of standard wheel spindles, and then take the universal jointsapart on each vehicle wheel; as to the front wheels, the ball joints andsteering arms are disconnected, and as to the rear wheels, thesuspension arms are unbolted. The vehicle is then crane-lifted intoplace and secured to the connecting means instead of to the wheels.

Terrain irregularities are simulated by vertical operation of thehydraulic rams serving as vertical supports 2,4,6,8. Actuation of therams can conventiently be programmed for operation by computer tosimulate any operation desired. For example, operation on a slope can besimulated by setting supports 2 and 6 a given amount higher or lowerthan supports 4 and 8;

other simulations will become apparent to persons skilled in the art.

As a given spindle rises or falls in relation to the rest of thevehicle, the spindle is allowed to respond in accordance with therequirements of the suspension geometry. The severity of the risedepends on the elevation of the bump and vehicle speed, and thehydraulic ram can be programmed to lift-the spindle at a ratecommensurate with the terrain and speed simulated. Except as aided bythe springs, fall of a vehicle wheel is free (gravitational), so it mayin some cases suffice to allow the hydraulic ram to lower under theinfluence of gravity, although I propose to power down.

To simulate the fore-andraft loading of striking an obstacle, thetwo-headed arrow f, FIGS. 1 and 5, represents a reciprocating forceinput capability, which is desirably also programmed into the computerthat controls the test. Preferably, this is accomplished throughhydraulic rams as aforesaid, connected through any one or all four ofthe fore-and-aft force input connectors such as those shown at 92 and 94in FIG. 2, the rams being connected at their other ends with thebuilding structure, such as the wall 16 shown in FIG. 1.

In most instances, the transverse force inputs can be accomplished bytilting the vehicle during test, i.e., by running with the verticalsupports on one side at a higher level than those on the other. If acloser control of transverse forces is desired, the invention is heredisclosed with a transverse force input capability represented bytwo-headed arrows t, FIGS. 1, 2, 3 and 4. Again, these inputs may beprovided by means of hydraulic rams even as the vertical force inputsare here shown as provided by hydraulic rams. The transverse forces areapplied to the vehicle through pairs of ears such as those shown at 104and 108, FIGS. 2, 3 and 4, having force input connectors such as the oneshown at 106 in FIG. 2. Again, to facilitate interchangeability ofparts, all the connectors 92, 94 and 106 are identical.

'input capability similar to 0, but about an axis which is the spindleaxis for each wheel, i.e., the axis of housings 32, 34, 36, and 38. Thepurpose of such a torque input capability is to provide a realisticcapacity to test the vehicle under load in terms of wheel drive, thusenabling simulation of constant speed load at any selected speed,acceleration, deceleration, braking, and the like. Torque inputs arethrough dynamometer couplings 110 and 112.

Reference is made now to the feature which permits wheel bearingadjustment with the vehicle in place on the fixture; see FIG. 8. Themechanic removes cap screws 176 and thus coupling 112. That providesaccess to polygonal end 186 of wrench 182. There is enough clearancebetween hub l and the inside diameter of tube 168 to allow the mechanicto loosen set screw 194 so that wrench 182 is free to turn in hub 190.After making the bearing adjustment, the mechanic retightens set screw194 and replaces coupling 112.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

I claim:

1. In means to mount a wheel drive including a powered spindle, anelement having an elongated cylindrical bore, said bore having an-axiscoincident with the axis of rotation of said spindle, means in one endof said bore to mount a pair of opposed axial thrust bearings which areadapted to support the wheel drive in said bore, said bearingsbeing-axially adjustable by turning one of two threaded elements havingthreaded engagement with each other in said wheel drive, means to turnsaid one threaded element from the bore end opposite said one end,comprising an elongated wrench having operative engagement with said onethreaded element and having an actuator extending through and ending atthe aforesaid opposite bore end, a hollow drive extension lying in saidbore between the bore and said wrench and secured in driving relation tothe wheel drive, and means disposed in the hollow of said driveextension for releasably securing the actuator against rotation relativeto said drive extension.

2. The invention set forth in claim 1, wherein said releasably securingmeans comprises an annular element surrounding the actuator, and atleast one set screw for holding said drive extension and the actuatoragainst relative rotation.

3. The invention as set forth in claim 1, and means supporting saidextension in the aforesaid opposite bore end for rotation relative tothe first-named ele ment.

1. In means to mount a wheel drive including a powered spindle, anelement having an elongated cylindrical bore, said bore having an axiscoincident with the axis of rotation of said spindle, means in one endof said bore to mount a pair of opposed axial thrust bearings which areadapted to support the wheel drive in said bore, said bearings beingaxially adjustable by turning one of two threaded elements havingthreaded engagement with each other in said wheel drive, means to turnsaid one threaded element from the bore end opposite said one end,comprising an elongated wrench having operative engagement with said onethreaded element and having an actuator extending through and ending atthe aforesaid opposite bore end, a hollow drive extension lying in saidbore between the bore and said wrench and secured in driving relation tothe wheel drive, and means disposed in the hollow of said driveextension for releasably securing the actuator against rotation relativeto said drive extension.
 2. The invention set forth in claim 1, whereinsaid releasably securing means comprises an annular element surroundingthe actuator, and at least one set screw for holding said driveextension and the actuator against relative rotation.
 3. The inventionas set forth in claim 1, and means supporting said extension in theaforesaid opposite bore end for rotation relative to the first-namedelement.